Electron discharge device and method



1967 r w. CARL ETAL 3,358,177

ELECTRON DISCHARGE DEVICE- AND METHOD Filed Oct. 12. 1964 QIN'VENTORS:

WILLIAM LQCARL,

JAMES c. HICKLE,

* TZQQQW THIR ATTORNEY. V

United States Patent 3,358,177 ELECTRON DISCHARGE DEVICE AND METHOD William L. Carl and James C. Hickle, Owensboro, Ky., assignorsto General Electric Company, a corporation of New York Filed Oct. 12, 1964, Ser. No. 402,991 16 Claims. (Cl. 313-292) ABSTRACT OF THE DISCLOSURE An insulative spacer member for an electron discharge device comprising a disc of natural mica, said mica having a plurality of irregular laminations defining interlaminate spaces, and relatively high conductive means for minimizing radiation from said spacer member substantially filling said interlaminate spaces.

This invention relates generally to electron discharge devices, and more particularly to such devices having improved insulative spacer discs.

In the manufacture of products such as electron discharge devices, a primary goal is to mass produce such devices, individual units of which have virtually identical electrical characteristics. A major problem long encountered in the manufacture of electron discharge devices, particularly damper diode tubes used in horizontal sweep circuits of television receivers, has been the extreme difficulty in attaining this goal. In the case of certain damper tube types, testing of identically manufactured tubes has revealed an extremely variant emission of unwanted electromagnetic radiation which has been found to originate in the insulative mica spacer discs. The exact mechanism which causes the micas to radiate is not fully understood but it is affected in some manner by the voltage impressed on the electrodes of the tube. Since the amount of radiation emitted by the micas has been found not to be consistent from one tube to another, it has heretofore been possible to provide acceptable tubes for damper diode operation only by 100% testing of the completed tubes. Such universal testing and selecting is extremely costly. Tube shields to overcome the harmful radiation have been proposed but these are also expensive and at best only partly reduce the radiation.

As modern television receivers have been designed subjecting the damper diodes'therein to successively higher voltages, two unwanted defects have been noted in the receiver which defects have been traced to the radiations from the insulative micas of damper diode tubes, These defects are: (1) a vertical white line of interference appears near the center of the picture and (2) the automatic gain control voltage increases which causes a resultant decrease in the sensitivity of the receiver.

In such modern receivers, the extremely high transient voltages produce such a large amount of radiation from the micas that a tube. shield has been found to be relatively ineffective to eliminate the spurious signal and the selection of tubes from a particular lot manufactured with standard micas have yielded only about a 5% acceptability. The use'of special high grade micas may yield about a 30% acceptability. It is, therefore, an object of this invention to provide an improved electron discharge device for this aforementioned use. It is another object of this invention to provide an insulator mica for. an electron discharge tube which substantially eliminates the above-described. defects by minimizing the unwanted micagenerated radiation thereby greatly improving the acceptability of such tubes for high voltage usage. Or, to put it another way, it is an object of this invention to provide an arrangement to greatly decrease the number of electron dischargedevice's which are rejected because of such harmful radiation eflects after assembly for use in television receivers.

It is a further object of this invention to provide an electron discharge device With insulative spacer members having improved electrical characteristics, which spacer mem bers may be readily and economically produced.

In accordance with a further aspect of the invention, it is an object to provide a novel method by which such spacers may be readily and economically produced.

In accordance with the objects of this invention there provided an electron discharge device having a mica insulative spacer mern-ber permeated with a material selected from the group including organic and inorganic silicates, phosphates, and borates, whereby the mica member is rendered incapable of radiating under the afore mentioned conditions. The mica members, in accordance with another feature of the invention, may be readily produced by treating the micas in a suitable solution, such as sodium silicate in a vacuum, so that the material permeates between the interlaminations of the mica structure.

Further objects and advantages of the invention will be understood from the following more complete description thereof, wherein:

FIG. 1 is a fragmentary perspective view of an electron discharge device illustrating a preferred embodiment of our invention; and

FIG. 2 is an enlarged cross-sectional view taken alon the line II-II in FIG. 1.

Referring to FIG. 1 there is shown an electric discharge device or electronic tube of the receiving tube type generally designated 1. From the outset, it is to be understood that our invention is not limited in application to the particular form of tube construction illustrated but is equally applicable to the many different and otherwise well-known types of devices wherein laminated mica members are employed for supporting and spacing elements of the device.

The electron discharge device 1 includes an evacuated envelope 2 containing a mount structure generally designated 3. The mount structure 3 comprises a pair of spaced insulative mica supports or support members 4, only one of which is shown. The supports 4 as seen in FIG. 2 are formed of single sheets of laminatedinsulative mica-mat terial. The supports 4 are adapted for supporting a plurality of cooperating electrode elements in insulated spaced relation by having end portions of the elements extending through apertures in the members 4. By way of example,

support rods 7 and an anode or plate 8, including inte-..

grally formed or suitably attached end portions 9.

In FIG. 2, .a portion of the insulative spacer member 4, is shown as consisting of three mica laminations 11, 12' and 13. It will be appreciated that in actual practice the spacer disc will consist of a body of interlaminated natural mica which may have many more laminations than the three shown. The irregular or non-planar nature of the laminations and the interlaminate spaces defined therebetween is exaggerated to show the permeation of a filler or coating material 14 into the interlaminate spaces. The materal 14 may completely fill these spaces or merely coat the interlaminate surfaces leaving holes as depicted at 15. Therefore, as used herein, the phrase, substantially fill, will be understood to mean either a coating of the interlaminate surface or a filling of the spaces, or both.

' In any case, there is provided a spacer member of intergroup of insulative materials including inorganic and organic silicates, phosphates and borates. For reasons of economy and availability, some of the preferred materials are ethyl silicate, colloidal silica, sodium silicate, sodium borate, borax and calcium phosphate. From this group the silicates, particularly sodium silicate, have been found to yield the best results, and are therefore preferred.

Since the exact mechanism causing the mica spacers to emit electromagnetic radiation is not fully understood, it is not known with certainty why the above-mentioned materials overcome or minimize such radiation, but it is believed to be because the group is insulative material having a higher electrical conductance characteristic than the mica. Therefore, relative to the mica, the materials may act as conductors providing a leakage path for a charge which ap ears to be accumulating in and between the mica laminations as a result of the high voltage transients to which the tubes are subjected.

The mica spacers may be treated by placing them individually or as a group in a solution containing a silicate, borate or phosphate, it being recognized that these materials may not be in true solution with some liquids but merely be in finely divided suspension. The viscosity of the solution may be adjusted by adding water or any suitable thinning liquid to obtain permeation of the mica in an expeditious manner. To speed the process and insure adequate permeation, the solution containing the mica may be placed under vacuum or pressure, in the latter case care being exercised so that excess pressure does not cause splitting apart of the mica laminations. Upon removal from the solution, the micas may be washed and dried. Firing of the micas at an elevated temperature, for example, 500 C., will insure that volatile materials which would adversely afiect operation of the finished tube are removed and also that the filler or coating material is firmly set in the interlaminate spaces. A more specific description of the method in accordance with the invention will be found in the following examples.

I Example I A plurality of mica insulator discs of the type used conventionally in tubes producing the troublesome radiations were placed in a solution of sodium silicate in distilled water. The solution was made of 5 parts sodium silicate solution having a viscosity of approximately 40 B6. and one part distilled water. To insure permeation into the laminations of mica discs, the solution containing discs was held under vacuum for a period totalling approximately five minutes. The discs were removed from the'solution and rinsed with distilled water to remove excess solution from the surface. The discs were then dried and fired to remove excess moisture and any material which would adversely atfect the operation of the tubes. The discs were used in manufacturing tubes in accordance with conventional techniques. These tubes were tested in a television receiver in which the lines of interference had been produced by the prior art tubes and were observed to have eliminated the lines of interference.

Example 11 Another group of mica insulator discs of the type used in the above example was treated in a solution of suitable viscosity of ethyl silicate using the same procedure of mica permeation as above. Tubes constructed using these discs were again observed to have improved the operation of the television receiver.

Examples III and IV The invention may be further carried out by using solutions of suitable viscosities, calcium phosphate and sodium borate, respectively, to treat mica discs. The same procedures as used in Examples I and II are carried out. The tubes constructed using micas treated in this manner may then be observed to improve the operation of the television receiver.

4 Example V Further, in accordance with the invention, a plurality of mica discs were treated in a solution of suitable viscosity of sodium silicate of the type disclosed in Example I. The solution containing the discs was then held in a pressure chamber at about p.s.i. for approximately five minutes. Upon removal from the chamber, the discs were cleaned, dried and fired as above. Upon testing, the radiation producing potential of the discs was greatly reduced.

From the above, it will be seen that there is provided an improved electron discharge device comprising an insulative spacer member of interlaminated mica having a filler or coating of material of the group consisting of organic and inorganic silicates, phosphates and borates permeated into or on the interlaminate spaces or surfaces. There is also provided a convenient and advantageous method of producing the same.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. An electron discharge device comprising an insula tive spacer disc of natural mica, said mica having a plu' rality of irregular laminations defining interlaminate spaces, and relatively high conductive means substantially filling said interlaminate spaces for minimizing radiation from said spacer disc.

2. An electron discharge device as recited in claim 1 wherein said means substantially filling said interlaminate spaces is a material selected from the group consisting of organic and inorganic silicates, borates and phosphates.

3. An electron dicharge device a recited in claim 1 wherein said means substantially filling said interlaminate spaces consists essentially of sodium silicate.

4. An electron discharge device comprising a pair of insulative spacer discs, said spacer discs being a natural mica having a plurality of irregular laminations defining interlaminate spaces, a plurality of electrodes supported in insulated spaced relation by said spacer discs, and relatively high conductive means substantially filling the interlaminate spaces for minimizing radiation emission of electromagnetic radiation from said spacer discs when said electrodes are subjected to high voltage.

5. An electron discharge device as recited in claim 4 wherein said means substantially filling said interlaminate spaces is a material selected from the group consisting of silicates, borates and phosphates.

6. An electron discharge device as recited in claim 4 wherein said means substantially filling said interlaminate spaces consists essentially of sodium silicate.

7. An electron dicharge device comprising an insulative spacer disc of natural mica, said mica having a plurality of irregular laminations defining interlaminate spaces, and means substantially filling said interlaminate spaces consisting essentially of a material selected from the group consisting of silicates, borates and phosphates.

8. An electron discharge device as recited in claim 7 wherein said means substantially filling said interlaminate spaces consists essentially of sodium silicate.

9. An insulative spacer member for an electron discharge device comprising a disc of natural mica, said mica having a plurality of irregular laminations defining interlaminate spaces, and relatively high conductive means for minimizing radiation from said spacer member subs'tantially filling said interlaminate spaces.

10. An insulative spacer member as recited in claim 9 wherein said means substantially filling said interlaminate spaces is a material selected from the group consisting of silicates, borates and phosphates.

11. An insulative spacer member as recited in claim 9 wherein said means substantially filling said interlaminate spaces consists essentially of sodium silicate.

12. An insulative spacer member for an electron discharge device comprising a disc of natural mica having a selected from the group consisting of silicates, borates and phosphates substantially filling the inteilaminate spaces.

13. An insulative spacer member as recited in claim 12 wherein said means substantially filling said interlaminate spaces consists essentially of sodium silicate.

14. A method of preparing an insulative natural mica spacer disc having a plurality of laminations defining interlaminate spaces for use in an electron discharge device comprising the steps of placing a spacer disc in a solution consisting essentially of a material selected from the group consisting of silicates, borates and phosphates for a length of time suflicient to allow said material to permeate into the interlaminate spaces, removing the excess solution from the surface of the member and drying and firing said disc.

15. A method of preparing an insulative natural mica spacer disc having a plurality of laminations defining interlaminate spaces for use in an electron discharge device comprising the steps of placing a spacer disc in a solution consisting essentially of a material selected from the group consisting of sodium silicate, ethyl silicate, colloidal silicate, sodium borate, borax, and calcium phosphate for a length of time sufficient to allow said material to permeate into the interlaminate spaces, removing the excess solution from the surface of the disc and drying and firing said member.

16. A method of preparing an insulative natural mica spacer disc having a plurality of laminations defining interlaminate spaces for use in an electron discharge device comprising the steps of placing a spacer disc in a solution consisting essentially of sodium silicate for a length of time sufficient to allow said material to permeate into the interlaminate spaces, removing the excess solution from the surface of the disc and drying and firing said disc.

References Cited UNITED STATES PATENTS 1,707,277 4/1929 Okuri 161163 1,975,080 10/1934 Boughton et a1. 16 1163 X 2,196,973 4/ 1940 Boughton 16l-171 2,231,718 2/ 1941 Hill 161'171 2,708,168 5/1955 Zachariason 313-268 X 2,865,426 12/1958 Heyman 161171 3,226,286 12/1965 Scheuer 161171 FOREIGN PATENTS 892,455 3/1962 Great Britain.

JOHN W. HUCKERT, Primary Examiner.

A. 1. JAMES, Assistant Examiner. 

1. AN ELECTRON DISCHARGE DEVICE COMPRISING AN INSULATIVE SPACER DISC OF NATURAL MICA, SAID MICA HAVING A PLURALITY OF IRREGULAR LAMINATIONS DEFINING INTERLAMINATE SPACES, AND RELATIVELY HIGH CONDUCTIVE MEANS SUBSTANTIALLY FILLING SIA INTERLAMINATE SPACES FOR MINIMIZING RADIATION FROM SAID SPACER DISC. 